A percutaneous gastrostomy involves the placement of a catheter within the stomach area of a living body. The latest procedures for performing a gastrostomy involve an initial percutaneous securement of the stomach to the abdominal wall. Once the stomach is fixed in place, a hollow needle is inserted through the skin and into the stomach area. Next, a "J" wire is introduced percutaneously into the stomach via the interior of the hollow needle. At this point, the "J" wire may be further positioned by use of a gastroscope and biopsy forceps. A hollow dilator/introducer is then inserted into the body with the "J" wire passing through its center.
A dilator/introducer is a multiple-piece device that comprises a pointed dilator needle partially housed within a close fitting elongated introducer tube. The front and rear ends of the introducer tube are flat with the plane of the openings being perpendicular to the longitudinal axis of the tube. When the introducer is mounted on the dilator, the front end of the introducer is located proximate the rear portion of the dilator's tapered point.
The dilator functions to gently spread the tissue away from the entry hole originally made in the body and thereby to allow the relatively large diameter introducer to pass through the hole with a minimum of resultant tissue trauma or damage. Once the introducer is properly positioned, the dilator is removed from the body and slid off the portion of the "J" wire that is exterior to the body. Next, a catheter is slid onto the exterior portion of the "J" wire and pushed into the body via the center passage of the hollow introducer tube. Once the catheter is in place, the introducer is gently pulled from the body. To remove the introducer from the catheter, the introducer is adapted to longitudinally split in half once pressure is applied to a pair of ear portions located at the rear of the introducer.
There are three problems that are experienced when using a conventional dilator/introducer apparatus.
The first problem is a tearing or traumatizing of the tissue during the insertion process. After the dilator initially spreads the tissue, portions of the tissue contact small gaps located between the front end of the introducer and the dilator. Depending on the size and shape of the gaps, the tissue can become trapped or torn. These gaps occur when the round shape of the forward end of the introducer does not contact the dilator for the full 360 degrees of the introducer's opening due to an improper or inexact machining of the two parts that make up the dilator/introducer. The machining problems are most noticeable with large bore introducers or cannulas that are sized to inwardly receive a large diameter stomach tube.
The second problem found with prior art dilator/introducers is that the front tip of the introducer acts as a stop during the insertion process. When dealing with large bore introducers, (for example, to receive a 6 mm. stomach tube) the wall thickness of the introducer must be great enough to prevent its being bent or broken during the surgical procedure. The shape of the introducer's opening in conjunction with its relatively large wall thickness requires the tissue to expand abruptly about the entire circumference of the introducer's tip when the introducer first contacts the tissue. The tip of the introducer effectively acts as a thick circular ridge about the dilator, which stops the smooth entry of the device into the body.
The third problem with a conventional dilator/introducer apparatus is that the physician must grasp the device in an awkward manner during the insertion process. A secure and comfortable grip is prevented by the "J"-wire's exiting from the flat rear face of the dilator portion. The physician cannot apply force directly against the rear end of the dilator portion lest a crimping of the "J" wire should result. Therefore, the device must be gripped only along its sides. This leads to a less secure grip on the device in which slippage may occur. Also, gripping the device between its ends is somewhat awkward and this reduces the effectiveness and control of the physician's pushing action when the device is inserted into the body.